Method and apparatus for using the sidelobe of a long range antenna for a short range communication link

Abstract

A communication satellite system (100) is established using one or more satellite constellations (110, 120). The two or more satellite groups (110, 120) are connected via long range crosslinks (145) which provide a communication path between the long range satellites (150, 170) in the two satellite groups (110, 120). Each satellite group (110, 120) comprises long range satellites (150, 170) and short range satellites (160, 180) which are interconnected using short range crosslinks (155, 175). A single antenna on each satellite provides both crosslinks. The long range crosslink (145) is established using the antenna's main beam and the short range crosslinks (155, 175) are established using the antenna's sidelobes.

What is claimed is: 
     
       1. A method of operating a satellite of a plurality of satellites comprising the following steps, not necessarily in the order shown: (a) receiving, at a first satellite, a signal;   (b) converting said signal into received data;   (c) determining if said received data contains long range data;   (d) processing said long range data when step (c) is true, wherein some of said long range data is processed into new long range data for a particular long range satellite;   (e) processing long range maintenance data when step (c) is false, wherein some of said long range maintenance data is processed into said new long range data;   (f) determining if said received data contains short range data;   (g) processing said short range data when step (f) is true, wherein some of said short range data is processed into new short range data for a particular short range satellite;   (h) processing short range maintenance data when step (f) is false, wherein some of said short range maintenance data is processed into said new short range data;   (i) combining said new long range data and said new short range data onto a single signal; and   (j) transmitting said single signal using a single antenna.   
     
     
       2. The method as claimed in claim 1 wherein step (b) further comprises the step of: using a receiver with a QPSK demodulator to convert said signal into said received data, wherein said received data is obtained from an in-phase port and a quadrature-phase port.   
     
     
       3. The method as claimed in claim 2, wherein said method further comprises the steps of: using said QPSK demodulator to obtain said long range data, wherein said long range data is obtained from said in-phase port when said short range data is obtained from said quadrature-phase port; and   using said QPSK demodulator to obtain said short range data, wherein said short range data is obtained from said in-phase port when said long range data is obtained from said quadrature-phase port.   
     
     
       4. The method as claimed in claim 1 wherein step (b) further comprises the step of: using a receiver with a CDMA demodulator to obtain said received data.   
     
     
       5. The method as claimed in claim 4 wherein said method further comprises the steps of: using said CDMA demodulator to obtain said long range data, wherein said long range data is obtained from a first code; and   using said CDMA demodulator to obtain said short range data, wherein said short range data is obtained from a second code.   
     
     
       6. The method as claimed in claim 1 wherein step (b) further comprises the step of: using a receiver with a frequency domain demodulator to obtain said received data.   
     
     
       7. The method as claimed in claim 6 wherein said method further comprises the steps of: using said frequency domain demodulator to obtain said long range data, wherein said long range data is obtained from a first subcarrier; and   using said frequency domain demodulator to obtain said short range data, wherein said short range data is obtained from a second subcarrier.   
     
     
       8. The method as claimed in claim 1 wherein step (b) further comprises the step of: using a receiver with a TDMA demodulator to obtain said received data.   
     
     
       9. The method as claimed in claim 8 wherein said method further comprises the steps of: using said TDMA demodulator to obtain said long range data, wherein said long range data is obtained from a first set of time slots in a TDMA waveform; and   using said TDMA demodulator to obtain said short range data, wherein said short range data is obtained from a second set of time slots in a TDMA waveform.   
     
     
       10. The method as claimed in claim 1 wherein step (i) further comprises the step of: using a transmitter with a QPSK modulator to combine said long range data and said short range data, wherein said long range data is used as in-phase data and said short range data is used as quadrature-phase data.   
     
     
       11. The method as claimed in claim 1 wherein step (i) further comprises the step of: using a transmitter with a QPSK modulator to combine said long range data and said short range data, wherein said short range data is used as in-phase data and said long range data is used as quadrature-phase data.   
     
     
       12. The method as claimed in claim 1 wherein step (i) further comprises the step of: using a transmitter with a CDMA modulator to combine said long range data and said short range data, wherein said long range data uses one code and said short range data uses another code.   
     
     
       13. The method as claimed in claim 1 wherein step (i) step further comprises the steps of: modulating a subcarrier signal using said long range data;   combining said subcarrier signal and said short range data into a new modulation signal; and   modulating a carrier signal using said new modulation signal.   
     
     
       14. The method as claimed in claim 1 wherein step (i) further comprises the steps of: modulating a subcarrier signal using said short range data;   combining said subcarrier signal and said long range data into a new modulation signal; and   modulating a carrier signal using said new modulation signal.   
     
     
       15. The method as claimed in claim 1 wherein step (i) further comprises the steps of: modulating a first subcarrier signal using said long range data;   modulating a second subcarrier signal using said short range data; and   modulating a carrier signal using said first subcarrier signal and said second subcarrier signal.   
     
     
       16. The method as claimed in claim 1 wherein step (i) further comprises the steps of: allocating a first set of time slots in a TDMA waveform for said long range data;   allocating a second set of time slots in said TDMA waveform for said short range data; and   modulating a carrier signal using said TDMA waveform.   
     
     
       17. The method as claimed in claim 1 wherein step (d) further comprises the following steps, not necessarily in the order shown: (d1) extracting position data from said long range data, wherein said position data describes a location for said particular long range satellite;   (d2) comparing said location for said particular long range satellite with a stored value of a last reported location for said particular long range satellite;   (d3) storing said location for said particular long range satellite as a new value of said last reported location for said particular long range satellite when step (d2) shows a difference;   (d4) extracting said new long range data from said long range data, wherein said new long range data contains data packets to be transmitted via a long range crosslink to said particular long range satellite;   (d5) determining, at said first satellite, a location for said first satellite;   (d6) comparing said location for said first satellite with a stored value of a last reported location for said first satellite;   (d7) storing said location for said first satellite as a new value of said last reported location for said first satellite when said step (d6) shows a difference;   (d8) calculating a new transmitting power for said long range crosslink to said particular long range satellite when said difference between said location for said first satellite and said location for said particular long range satellite exceeds a predetermined threshold;   (d9) storing said new transmitting power, if said new transmitting power was calculated;   (d10) calculating a new main beam direction for said long range crosslink to said particular long range satellite when said location for said first satellite and said location for said particular long range satellite have changed more than a predetermined value; and   (d11) storing said new main beam direction, if said new main beam direction was calculated.   
     
     
       18. The method as claimed in claim 1 wherein step (g) further comprises the following steps, not necessarily in the order shown: (g1) extracting position data from said short range data, said position data describing a location for said particular short range satellite;   (g2) comparing said location for said particular short range satellite with a stored value of a last reported location for said particular short range satellite;   (g3) storing said location for said particular short range satellite as a new value of said last reported location for said particular short range satellite when step (g2) shows a difference;   (g4) extracting new short range data from said short range data, wherein said new short range data contains data packets to be transmitted via a short range crosslink to said particular short range satellite;   (g5) determining, at said first satellite, a location for said first satellite;   (g6) comparing said location for said first satellite with a stored value of a last reported location for said first satellite;   (g7) storing said location for said first satellite as a new value of said last reported location for said first satellite when step (g6) shows a difference;   (g8) calculating a new required omni power for said short range crosslink to said particular short range satellite when said difference between said location for said first satellite and said location for said particular short range satellite exceeds a predetermined threshold;   (g9) storing said new required omni power, if said new required omni power was calculated;   (g10) determining if omni power is sufficient for said short range crosslink to said particular short range satellite; and   (g11) reporting a failure for said short range link when step (g10) is false.   
     
     
       19. The method of operating a satellite in a satellite system comprising the steps of: transmitting a first set of signals using a crosslink device via a long range crosslink with a first satellite in said satellite system which is located far from said satellite;   using said crosslink device to transmit a second set of signals via a short range crosslink with a second satellite which is located near to said satellite, wherein said first set of signals and said second set of signals are combined into a single transmitted signal, said long range crosslink being established using a main beam in a radiation pattern of said crosslink device, and said short range crosslink being established using a sidelobe in the radiation pattern of said crosslink device;   receiving a third set of signals using said crosslink device via long range crosslinks with a third number of satellites in said system which are located far from said satellite; and   using said crosslink device to receive a fourth set of signals via short range crosslinks with a fourth number of satellites which are located near to said satellite, wherein said third set of signals and said fourth set of signals are obtained from a single received signal.   
     
     
       20. A satellite in a communication system comprising: a crosslink device which allows said satellite to communicate with short range satellites in said communication system which are located close to said satellite and which also allows said satellite to communicate with long range satellites in said communication system which are located far from said satellite;   a transmitter coupled to said crosslink device which allows said satellite to transmit a first set of signals to a first number of said long range satellites and which also allows said satellite to transmit a second set of signals to a second number of said short range satellites substantially at the same time; and   a receiver coupled to said crosslink device which allows said satellite to receive a third set of signals from a third number of said long range satellites and which also allows said satellite to receive a fourth set of signals from a fourth number of said short range satellites, wherein said transmitter comprises: a data processor for processing short range data and long range data;   a quadrature phase shift keyed (QPSK) modulator coupled to said data processor for modulating said short range data into said third set of signals and for modulating said long range data into said fourth set of signals;   an up converter coupled to said QPSK modulator for up converting said third and fourth sets of signals;   a filter coupled to said up converter for filtering said third and fourth sets of signals;   a power amplifier coupled to said filter for amplifying said third and fourth sets of signals; and     duplexor coupled to said crosslink device and to said power amplifier for separating said first set of signals and said second set of signals from said third set of signals and said fourth set of signals, respectively.   
     
     
       21. The satellite as claimed in claim 20, wherein said crosslink device is provided by a laser signal means. 
     
     
       22. The satellite as claimed in claim 20, wherein said crosslink device is provided by an RF signal means. 
     
     
       23. The satellite as claimed in claim 20, wherein said crosslink device is provided by an RF antenna means. 
     
     
       24. The satellite as claimed in claim 20, wherein said receiver further comprises: an antenna assembly for receiving said third set of signals and for receiving said fourth set of signals;   a duplexor coupled to said antenna assembly for separating said first set of signals and said second set of signals from said third set of signals and said fourth set of signals;   a filter coupled to said duplexor for filtering said third set of signals and said fourth set of signals;   an amplifier coupled to said filter for amplifying said third set of signals and said fourth set of signals;   a down converter coupled to said amplifier for down converting said third set of signals and said fourth set of signals;   an intermediate frequency (IF) filter couple to said down converter for filtering said third set of signals and said fourth set of signals;   a quadrature phase shift keyed (QPSK) demodulator coupled to said IF filter for demodulating said third set of signals into long range data and for demodulating said fourth set of signals into short range data;   a data processor coupled to said QPSK demodulator for processing said short range data and said long range data; and   a frequency source coupled to said down converter and to said QPSK demodulator.